Let's take a look at some of best imouto's best moments in the anime, starting with how Tanjiro would be completely screwed without her.
I totally got lazy and didn't subtitle these, but you don't need to understand the dialogue to understand Nezuko's greatness:
Nezuko used High Jump Kick. It's super-effective!
Messi's got nothing on her.
Surprise!
She kicked him so hard his head started spinning. Literally.
A literal soccer prodigy.
There isn't a goalie alive that can stop that last kick.